Read the following passage and answer, based on it.

On a surface which is free from obstacles, such as a clear road or path, only two or three species of snakes can hope to catch up with a human being, even if they are foolish to try. A snake seems to move very fast but its movements are deceptive. In spite of the swift, wave-like motions of its body, the snake crawls along the ground at no more than the speed of a man's walk. It may, however, have an advantage inside a jungle, where the progress of a man is obstructed by thorny bushes. But in such places, the footsteps of a man are usually more than enough to warn snakes to keep away. Although they have no ears of the usual kind, they can feel slight vibrations of the ground through their bodies, and thus get an early warning of danger.